Safety device for small gasoline engines

ABSTRACT

In a single cylinder gasoline engine having a high tension lead which extends across a sheet metal blower shroud extension on the cylinder head and terminates in a clip normally attached to a terminal on top of the spark plug, the shroud extension has a Ushaped slot that defines a finger. When removed from the spark plug terminal the clip is engaged with the finger to be held thereby against coming near the plug terminal, preventing any possibility of inadvertent starting.

United States Patent [191 Gumtow [4 1 June 12,1973

1 1 SAFETY DEVICE FOR SMALL GASOLINE ENGINES [75] Inventor: Herbert A. Gumtow, Brookfield,

Wis.

[73] Assignee: Briggs & Stratton Corporation,

Wauwatosa, Wis.

[22] Filed: May 15, 1972 [21] Appl. No.: 253,156

[52] U.S. Cl. 123/169 R, 123/198 D, 123/198 R [51] Int. Cl... F02p 11/00, F02p 13/00, F02b 77/08 [58] Field of Search 123/169 R, 169 PH,

123/148 S, 198 D, 198 B, 198 E, 198 R, 195

C, 195 P, 179 SE [56] References Cited UNITED STATES PATENTS 1,151,001 10/1924 Padden 123/169 R X Meredith... 123/169 PH Casey 123/198 B Primary ExaminerAl Lawrence Smith Att0rney-Ira Milton Jones [57] ABSTRACT In a single cylinder gasoline engine having a high tension lead which extends across a sheet metal blower shroud extension on the cylinder head and terminates in a clip normally attached to a terminal on top of the spark plug, the shroud extension has a U-shaped slot that defines a finger. When removed from the spark plug terminal the clip is engaged with the finger to be held thereby against coming near the plug terminal, preventing any possibility of inadvertent starting.

2 Claims, 2 Drawing Figures PATENTEU JUN 1 2|915 SAFETY DEVICE FOR SMALL GASOLINE ENGINES This invention relates to safety devices for internal combustion engines such as are used for powering lawn mowers and similar machines, and the invention is more particularly concerned with means for so holding the high tension lead of such an engine, when it is disconnected from the spark plug, as to prevent any possibility of inadvertent firing of the engine.

Engines of the type with which this invention is concerned are installed on a wide variety of machines, all of which tend to pose the problem to which this invention is directed. But the problem is a particularly serious one with rotary power lawn mowers, and since such machines are familiar to almost everyone, the invention will be described, by way of example, with particualar reference to rotary lawn mowers. However, it will be understood that the invention can be advantageously incorporated in any and all small gasoline engines, regardless of the end uses for which they are intended.

It is safe to say that every rotary lawn mower must be turned on its side at one time or another, to permit access to the underside of its deck, either for cleaning matted grass off the inner surface of the rotor housing, or for changing or sharpening the blades. Almost invariably, too, it is necessary on such occasions to rotate the sharp bladed rotor through at least part of a revolution, thereby, in effect, cranking the engine.

Reasonable caution at such times dictates not only that the ignition control be in its off position, but also that the high tension lead be disconnected from its terminal on the spark plug and moved to a position in which its clip is well spaced from that terminal, so that the spark plug cannot fire when the engine is cranked, even if the ignition should be inadvertently switched However, as many lawn mower operators are aware, the precaution of disconnecting the spark plug lead has often been defeated by the character of the lead itself. The high tension lead is relatively stiff and thick, and during the long periods when it is attached to the plug it takes a set such that, when disconnected, itsclip tends to move back to a position alongside the spark plug terminal. Thus a person who disconnected the high tension lead from the spark plug in preparation for work on the underside of the mower was often shocked to find, upon turning the mower back upright, that the clip on the high tension lead had been close enough to the plug terminal to allow the plug to be fired.

The condition just described had at least the appearance of being extremely dangerous. No actual accidents are known to have been caused by it, probably because the occurrence of actual plug firing was dependent upon the unlikely coincidence that the high tension lead clip had to be in dangerous proximity to the plug terminal at the same time that the ignition switch was on and the engine crankshaft was turned over fast enough to cause a powerful spark to be produced. Nevertheless, the condition offered a source of serious phsychological discomfort, even it it posed an actual safety hazard only under very unusual conditions.

Heretofore no really satisfactory solution to this problem has appeared on commercial engines. The lack of reported accidents may have encouraged a feeling that nothing needed to be done, but the small engine and power lawn mower industries have for a long time evidenced great concern about all safety aspects of their products. More likely, the reason was that the obvious expedients for solving the problem are not sufficiently inexpensive and convenient to warrant their adoption. There is little advantage to the customer in providing a safety feature that so adds to the cost of a product or so detracts from its appearance that he elects to buy a competitive product which does not include that feature, nor does he benefit from a safety feature which invovles such inconvenience in its use that he prefers not to take advantage of it even when it is present.

By contrast, it is an object of this invention to provide a safety device for small engines which can be made at little or no cost, does not detract from the appearance of the engine, and does not present any protuberance on the engine or cause any incomvenience with respect to installation or use of the engine, which safety device securely but readily releasably retains the clip on the high tension lead when that clip is removed from its terminal on the spark plug, holding it in a safe, convenient position well spaced from the terminal.

It is also an object of this invention to provide a safety device that is so convenient to use that it is almost easier to take advantage of it than to disregard it.

The objects of the invention are achieved by the simple expedient of providing a slot in a sheet metal member that is conventionally secured to the engine cylinder head for cooperation with other parts of the engine to direct cooling air across the cylinder head.

With these observations and objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawing, which exemplify the invention, it being understood that changes may be made in the specific apparatus disclosed herein without departing from the essentials of the invention set forth in the appended claims.

The accompanying drawing illustrates one complete example of an embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIG. 1 is a perspective view of the cylinder head portion of a small gasoline engine equipped with the safety device of this invention, and with the clip on the high tension lead disconnected from the spark plug terminal and attached to the safety device; and

FIG. 2 is a plan view of the blower shroud extension having the safety device of this invention.

Referring now to the accompanying drawing, the numeral 5 designates generally'the cylinder head portion of a single cylinder gasoline engine. Although the engine flywheel is not shown, those skilled in the art will at once recognize that it is equipped with blower vanes by which its rotation is caused to produce a stream of cooling air, inasmuch as the drawing shows a part of the conventional shroud or hood 6 which directs air from the flywheel blower across the engine body and which encloses the blower and a substantial part of the cylinder.

The cylinder head 7, which is formed separately from the main part of the body and is secured thereto by means of bolts 8, is provided with integral cooling fins 9. The cylinder head has in it a threaded hole that accommodates a spark plug 10.

As is conventional, the magneto (not shown) that serves as the source of high voltage ignition current is located in the vicinity of the flywheel, and a relatively heavy, well insulated high tension lead 12 extends along the cylinder body and across the cylinder head, terminating in a clip 13 that normally is readily detachably secured to a concentric stud-like terminal 14 on the top of the spark plug.

Overlying the cylinder head at one side of the spark plug is a stamped sheet metal member 15 that forms an extension of the blower shroud 6 and is fastened to the cylinder head by certain of the bolts 8' that secure the cylinder head to the cylinder body. The shroud extension 15 is held in edge-to-edge relation to the shroud proper and it and the shroud have opposing semicircular notches in their adjoining edge portions that cooperate to define a hole 16 through which the high tension lead 12 extends.

The safety device of this invention comprises a tab or finger 17 which is integral with the shroud extension 15 and which is defined by a U-shaped cut-out or slot 18 in that member. Preferably the slot has legs which converge towards its bight portion to some extent, so that the finger 17 that it defines is somewhat wedge like.

Note that the finger or tab is substantially coplanar with the remainder of the shroud extension 15, and therefore its presence does not cause any protuberance or projection on the engine.

Attention is also directed to the fact that the finger or tab 17 points generally toward the hole 16 through which the high tension lead extends. Hence, when the high tension lead is disconnected from the spark plug, its terminal engaging clip 13 can be slipped over the finger, and the restoring forces in that lead that otherwise tend to bring the clip back into proximity to the spark plug terminal 14 will instead force the clip into more secure engagement with the finger.

The slot 18 that defines the finger 17 should of course be wide enough to accommodate wall portions of the clip 13 when the latter is engaged with the finger, but otherwise neither the size nor the shape of the slot is critical.

From the foregoing description taken with the accompanying drawings it will be apparent that this invention provides an extremely simple, inexpensive and effective safety device for small gasoline engines whereby the high tension lead termina clip is kept well clear of the spark plug terminal when said clip is re moved from said terminal, and which device encourages safe practices by reason of the fact that it is extremely convenient to use.

Those skilled in the art will appreciate that the invention can be embodied in forms other than as herein disclosed for purposes of illustration.

The invention is defined by the following claims:

1. An internal combustion engine for powering a machine such as a lawn mower, said engine having a cylinder head in which there is a spark plug with an exposed terminal, a high tension lead which terminates in a clip that is detachably securable to said terminal, and a sheet metal shroud member that extends across a portion of the cylinder head and cooperates with other parts on the engine to direct cooling air across the cylinder head, and across which the high tension lead normally extends, said engine being characterized by:

said shroud member having a U-shaped slot therein that defines a prong with which the clip on the high tension lead is engageable when said clip is removed from the terminal and whereby said clip is held spaced a sufficient distance from the terminal to prevent any possible inadvertent starting of the engine at times when work is being done around driven parts of a machine powered by the engine.

2. An internal combustion engine for powering a machine such as a lawn mower, said engine having a cylinder head in which there is a spark plug with an exposed terminal, a high tension lead which terminates in a clip that is detachably securable to said terminal, and a sheet metal shroud member that extends across a portion of the cylinder head and cooperates with other parts of the engine to direct cooling air across the cylinder head, and across which the high tension lead normally extends, said engine being characterized by:

means on said shroud member defining a tab integral therewith and substantially coplanar with adjacent portions thereof, said tab being of a width and length to engage the clip on the high tension lead, and projecting in a direction such that the clip tends to be maintained engaged with the tab by resilient flexing force exerted by the high tension lead, said tab being useable to secure the clip at times when it is removed from the terminal so that the clip is then spaced sufficiently far from the terminal to prevent any possibility of a spark jumping thereto and causing inadvertent starting of the engine. 

1. An internal combustion engine for powering a machine such as a lawn mower, said engine having a cylinder head in which there is a spark plug with an exposed terminal, a high tension lead which terminates in a clip that is detachably securable to said terminal, and a sheet metal shroud member that extends across a portion of the cylinder head and cooperates with other parts on the engine to direct cooling air across the cylinder head, and across which the high tension lead normally extends, said engine being characterized by: said shroud member having a U-shaped slot therein that defines a prong with which the clip on the high tension lead is engageable when said clip is removed from the terminal and whereby said clip is held spaced a sufficient distance from the terminal to prevent any possible inadvertent starting of the engine at times when work is being done around driven parts of a machine powered by the engine.
 2. An internal combustion engine for powering a machine such as a lawn mower, said engine having a cylinder head in which there is a spark plug with an exposed terminal, a high tension lead which terminates in a clip that is detachably securable to said terminal, and a sheet metal shroud member that extends across a portion of the cylinder head and cooperates with other parts of the engine to direct cooling air across the cylinder head, and across whiCh the high tension lead normally extends, said engine being characterized by: means on said shroud member defining a tab integral therewith and substantially coplanar with adjacent portions thereof, said tab being of a width and length to engage the clip on the high tension lead, and projecting in a direction such that the clip tends to be maintained engaged with the tab by resilient flexing force exerted by the high tension lead, said tab being useable to secure the clip at times when it is removed from the terminal so that the clip is then spaced sufficiently far from the terminal to prevent any possibility of a spark jumping thereto and causing inadvertent starting of the engine. 